Prevalence and prognostic value of elevated urinary albumin excretion in patients with asthma: analysis of NHANES 2001–2018

BACKGROUND: Elevated urinary albumin excretion, quantified as the urinary albumin-to-creatinine ratio (UACR), is a marker of endothelial injury and chronic kidney disease. This study investigates the prevalence and prognostic significance of elevated UACR in asthma patients. METHODS: Using data from the National Health and Nutrition Examination Survey (NHANES 2001-2018), 6,930 adults with asthma were analyzed. Participants were stratified by UACR categories: < 30 mg/g (Group 1), 30-300 mg/g (Group 2), and ≥ 300 mg/g (Group 3). Furthermore, for Group1, we further divided it into tertiles. Kaplan-Meier curves, Cox proportional hazards models, restricted cubic splines, and subgroup analyses were employed to assess associations between UACR and mortality. RESULTS: Among 6,930 adults with asthma, 809 all-cause and 195 cardiovascular deaths occurred. Elevated UACR was prevalent in 12.6% (Group 2: 10.5%, Group 3: 2.1%). Compared to Group 1, Group 3 had a higher risk of all-cause mortality (HR: 2.60, 95% CI:1.44-4.71) and cardiovascular mortality (HR: 2.50, 95% CI:1.13-5.55) after full adjustment. Even within the normal range (UACR < 30 mg/g), the highest tertile (Tertile 3) exhibited increased all-cause mortality (HR: 1.69, 95% CI:1.10-2.59). Restricted cubic splines revealed a linear dose-response relationship between UACR and mortality (P for nonlinearity > 0.05). Subgroup analyses confirmed consistency across age, sex, BMI, and comorbidity strata. CONCLUSIONS: Elevated UACR is independently associated with higher all-cause mortality in adults with asthma, even at levels below the traditional threshold for albuminuria. These findings underscore UACR as a prognostic biomarker for risk stratification in asthma management.